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Full text of "Soft Circuits"

Plush Irradiated Sirloin 



.[ 



Make Projects 



build, hack, tweak, share, discover. 



Plush Irradiated Sirloin 



Written By: Becky Stern 



TOOLS: 



Arduino IDE software (1) 

Computer (1) 

Hot glue gun (1) 

Iron (1) 

Ironing board (1) 

Pliers (1) 

Sewing machine (1) 

Sewing needle (1) 

Sewing pins (1) 

Soldering iron (1) 

USB A-B cabled) 

Wire cutters (1) 



© PARTS: 

360° LEDs(16) 

Transistor (2) 

Solderless breadboard (1) 
and/or solder-type breadboard 

Solder (1) 

Fabric (1) 

or silk-screen your own 

Thread (1) 

Polyester fiberf ill (1) 
plush stuffing 

Arduino microcontroller (1) 

AC adapter (1) 

Toggle switch (1) 
optional 

Epoxy (1) 
or hot glue 

Hook-up wire (1) 



SUMMARY 

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Page 1 of 6 



Plush Irradiated Sirloin 



Faced with an assignment to make a plush night light, I thought, "Why light?" and 
brainstormed reasons for a stuffed toy to light up. In a glowworm toy, for instance, the light 
mimics nature. I'd been reading Michael Pollan's The Omnivore's Dilemma, and this got me 
thinking about the chain of refrigeration, labor, and irradiation involved in American beef 
production. So I thought, glowing irradiated meat! I know that irradiated meat doesn't glow, 
and neither does toxic waste unless it's in a cartoon, but plush toys typically represent 
cartoon characters anyway, so it made sense: Plush Irradiated Sirloin. 



Step 1 — Prepare the fabric. 




• I silk-screened my steak illustration onto pink flannel and sewed the pieces together 
(inside out, so the seams wouldn't show), leaving a small opening at the base of each one. 
(For an excellent primer on silk-screening, check out CRAFT magazine, Volume 01, page 
106.) You can also use pre-patterned fabric or use fabric paint to hand-paint the design. 
Next, I turned them right side out, but left them empty. I had to put the lights inside before I 
stuffed the plush fiberfill around them! 

• Grab the silkscreen template: http://makezine.com/11/diyhome steak/ 







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Page 2 of 6 



Plush Irradiated Sirloin 



Step 2 — Add the Arduino board. 



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Plush Irradiated Sirloin 




Grab the code: 
http://makezine.com/11/diyhome_steak/ 

Inside, each steak has two 360° 
super-bright LEDs wired in series. 
These have frosted lenses that 
distribute the light evenly in all 
directions, making them perfect for 
the inside of plush toys. Because I 
wanted the steaks to glow dimmer 
and brighter periodically, I needed 
some kind of signal to control the 
brightness of the lights. The 
Arduino board, my favorite 
microcontroller solution lately, 
supports the perfect feature for 
this: pulse width modulation 
(PWM). PWM can make LEDs, 
which are binary, appear dimmer 
by pulsing them on and off, with 
varying time ratios, faster than the 
human eye can see. 

The PWM signal controls the glow, 
but the Arduino can only output up 
to 5V, which isn't high enough to 
power these super-bright LEDs. I 
had planned to power the Arduino 
with a 12V AC adapter, so I 
designed the circuit to drive the 
LEDs from the same source. I used 
2 TIP 120 transistors to amplify the 
signal to each half of the meat tray, 
4 steaks each. This pumps the 
circuit's full 12V through 2 parallel 
sets of 2 LEDs (2 steaks, 4 LEDs) 
in series, which works out to 3V 
per LED. 



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Page 4 of 6 



Plush Irradiated Sirloin 



Step 3 — Add the LEDs 




• For each steak, I made an LED insert with 2 LEDs wired in series and neatly twisted. I 
spaced the LEDs about 4" apart, so that they would each light up an even half of the steak 
without being too close to the edges. I made the lead wires really long, and I knew they 
would be exposed, so I chose red and white wire to match my plush. 

• After wiring up the circuit and soldering and testing the LEDs, I finally assembled the 
steaks. It's important to make sure all your LEDs are functioning properly first; it's no fun 
to debug a sewn-together toy. Since electronics with fabrics could be a fire hazard, I 
covered the LED leads in epoxy (hot glue works, too) to prevent a potentially dangerous 
short. 

• I positioned each double-LED wire inside a steak, and filled around it with polyester filling. I 
left the LEDs plugged in, so I could see how the light diffused and adjust them accordingly. 
When I got them how I wanted, I stitched up the bottom openings by hand, and arranged 
them together on a tray. 



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Plush Irradiated Sirloin 



Step 4 — Bask in the glow. 




# Each half of the tray (4 steaks) 
glows in alternation with the other. 
The pattern is subtle and soothing, 
the way a good nightlight should 
be. They're soft, but not very 
cuddly, as they remain tethered to 
their circuit board. In the future I 
could embed smaller circuit boards 
inside each steak to make a 
portable, more snuggly version. 
I've also been thinking of making a 
larger version for throw pillows, or 
a smaller version with catnip 
instead of electronics. These 
steaks have been great 
conversation starters in the 
classroom and online, and I hope 
they inspire people to learn about 
the politics of our food industry. 



This project first appeared in MAKE Volume 11 . 

This document was last generated on 201 2-1 1 -03 02:38:42 AM. 



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Page 6 of 6